1. Field of the Invention
This invention relates to laminitis in animals. More specifically, the invention comprises a method of treating the sequela of laminitis in animals, particularly horses.
2. Description of the Related Art
Laminitis is a serious medical condition in horses and other hoofed animals, and despite significant advances in veterinarian medicine, remains a major reason for euthanasia of such animals. Laminitis is an inflammation of the lamina (the lamellar attachment between the distal phalanx (coffin bone) and the inner hoof wall. Laminitis is characterized by separation of the hoof wall from the distal phalanx due to the deterioration and detachment of the lamina, which holds the two together. Failure of the laminar attachments, in a majority of cases is limited to the toe region (commonly called rotation). It is hypothesized that without the distal phalanx properly attached to the inside of the hoof wall, the weight of the horse and the forces of locomotion by the deep digital flexor tendon cause the distal phalanx to rotate away from the hoof capsule. This process shears the vasculature and crushes the corium (dermis) of the sole, causing unrelenting pain and a characteristic lameness. Radiographic and necropsy examination of the feet of affected horses show a characteristic rotation of the dorsal border of the distal phalanx away from the dorsum of the hoof wall.
In more rare and significantly more severe cases the failure of attachment can extend around the perimeter of the hoof. This allows the entire bony column to drop within the hoof capsule.
Laminitis can occur secondary to many diseases of the horse, but is common following overeating, colic, fever, shock, pneumonia, injury and obesity.
All hoofed animals, and particularly horses, are susceptible to laminitis and significant economic loss occurs due to severe pain and debilitation of these animals. Due to the insidious nature of the disease process, damage to the laminae often occurs prior to clinical evidence of abnormality.
There is no cure for laminitis. Current medical therapies include identification and treatment of the underlying disease, systemic anti-inflammatory medications and rest. A more aggressive treatment of the sequela of laminitis involves severing the deep digital flexor tendon. Additionally, support of the sole has met with some success utilizing deep sand flooring, peat moss and foam sole pads.
One example of treatment is the application of wedge shoes. Elevation of the heels with wedge shoes reduces the pull of the deep digital flexor tendon on the coffin bone and therefore decreases the stress on the dorsal laminar attachment. However, there are several disadvantages to the wedge shoe therapy. First, the wedge shoe creates additional stresses on other regions of the foot and may cause compression of the hoof capsule during the acute phase. The second disadvantage to wedge shoes involves the method of attaching the wedge shoe to the hoof. If wedge shoes are nailed onto the hoof, the hoof capsule may be compressed, due to the nailing force, potentially leading to further damage. If wedge shoes are glued onto the hoof the horse may be forced to hold one foot up for an extended period of time thereby harming the opposite foot. To reduce risk of further damage it is recommended that wedge shoes are bandaged to the foot during the acute phase. However, if the bandaged shoe slips from the hoof it could cause an abrupt strain on the deep digital flexor tendon and potential further damage to the dorsal laminar attachment. Another disadvantage to wedge shoes is the risk of increased damage if the angle of the wedge does not correspond to each horse's particular condition. Wedge shoes must be designed for each horse on a case by case basis based on the severity of the condition or based on the hoof's adaptation to the condition before any treatment was given. In order to properly treat the condition different horses may require the wedge shoes to be adjusted to different angles. If the angle of the wedge is improper the condition may become more severe.
Surgical transection of the deep digital flexor tendon (DDFT) has also been used to reduce the shearing forces during the acute phase of laminitis. One study reported a 60% survival rate at 2 years after the procedure. Those animals who do recover from the severing of the deep digital flexor tendon are usually not comfortable enough to ride. Even with these issues in mind, current veterinary practices suggest that a deep digital flexor tenotomy is the fastest way to counteract the rotational forces and restore the perfusion and tissue mass to the dorsal regions of the foot.
Accordingly, there is a need for a proactive treatment that effectively treats and/or prevents the laminitis and its sequela. This treatment would effectively treat these conditions without requiring invasive surgery and all the risks and side effects associated with such invasive surgery.